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MINI 02 - Immunotherapy (ID 92)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:P. Forde, S.J. Antonia
- Coordinates: 9/07/2015, 10:45 - 12:15, Four Seasons Ballroom F3+F4
MINI02.01 - Pulmonary Large Cell Carcinoma and Solid Adenocarcinoma Are Highly Mutated with Frequent Expression of PDL1 (ID 2257)
10:45 - 12:15 | Author(s): A. Perry
Large cell carcinoma (LCC) is an uncommon lung tumor that arises predominantly in smokers and shares many features of solid adenocarcinoma (ADC). 40% of LCC/solid ADC harbor mutations in KRAS; EGFR and ALK alterations are rare in this tumor type. The majority of these tumors, however, lack one of the commonly queried oncogenic driver alterations, thus therapeutic options are limited for patients with this tumor type. Immunomodulatory therapies, including targeting PDL1, have shown promise in a variety of tumor types. Tumor neo-antigens, including those induced by smoking, are associated with mutational burden and may predict susceptibility to cytolytic immune response; in addition, high PDL1 expression in non small cell lung carcinoma has been associated with response to anti-PDL1 drugs. Given the high prevalence of smoking in patients with LCC and solid ADC, we hypothesize that these tumors may be amenable to immunomodulatory therapy and sought to define the frequency of PDL1 expression in tumors lacking an oncogenic driver mutation.
This study was restricted to 27 LCC and solid ADC known to be negative for KRAS, EGFR, ALK and ROS1 alterations. Hybrid capture targeted next generation sequencing (NGS) on an Illumina HiSeq 2500 was performed using a cancer genomic assay to detect mutations, copy number variations (CNVs) and structural variants. The assay captures exonic sequences of 275 cancer genes and 91 introns across 30 genes for rearrangement detection. Findings were compared to an institutional cohort of 732 consecutive lung tumors sequenced on the same platform. Immunohistochemistry for PDL1 was performed using a rabbit monoclonal antibody (Cell Signaling Technologies) at 1:100 dilution following pretreatment with citrate buffer/pressure cooker and detected using the Envision + polymer system (DAKO). Immunostaining was considered positive in the tumor component or the inflammatory component if ≥5% of the cells showed membranous staining.
Of the 27 tumors tested, 26 were resected from smokers. NGS revealed an average of 14.9 mutations per case for LCC/solid ADC cohort versus 8.1 mutations in the overall cohort of lung tumors (p<0.0001). 11 cases (41%) were positive for PD-L1. 7 cases (26%) showed strong, diffuse staining (≥70% of cells) for PD-L1. The inflammatory component was positive for PD-L1 in 25 cases (93%). Two cases with strong expression of PD-L1 by immunohistochemistry (>90% of cells) showed focal amplification of CD274 by NGS.
LCC and solid ADC are strongly associated with a smoking history and harbor a significantly higher average mutational burden than other lung tumors. 41% of LCC/solid ADC are positive for PDL1 by immunohistochemistry with 26% showing very strong PDL1 expression and nearly all cases showing some degree of positivity in the associated inflammatory infiltrate. In some cases, high PDL1 expression is associated with focal amplification of CD274, the gene encoding PDL1. These findings suggest that LCC/ solid ADC is likely to have smoking-associated neo-antigen expression and that PDL1-directed immunotherapies may be a promising therapeutic approach in this otherwise poorly-characterized lung tumor.
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